Cutter.



w. cFARNuII/I.

CUTTER.

APPLICATION FILED MAY 24. IQII.

Patented Mar. 4,1919, zsIIEETs-sHEEr 2 'lates to cutters, and more particularl sion of power. One of the objects of the present invention y WILLIAM C. FARNUM, OF WINCHENDON,

a; ornibn.

MASSACHUSETTS.

GUTTER.

teeth of gears is so constructed that it cutsthe concave prole of a tooth on an arc having a radius shorter than the radius of the arc of the convex profile of thetooth. 'As a consequence, when two such gears intermesh, the convex profile of a tooth of onef the gears will not accurately fit' and conform to the contourl of the vconcave profile of a tooth of the other gear, and the full strength of the teeth is not utilized in the transmisis to provide a spiral cutter whereby teeth ,are formed,.each having concave and convex profiles of the same curvature. The construction of the curved-teeth produced 1s such that the teeth of inter-'meshing gears may accurately engage throughout the entire Iextent of the arcs crossin their pitch circles and gears with power ul transmission, long life and quiet operation are as-` sured. I f

The usual spiral cutter is so. constructed that it makes cuts simultaneously on the con# cave and convex profiles ofthe teeth.

Another object of the invention is to provide a spiral cutter which makes'a cut along one profile and then along the other profile. In other words, the concave and. convex cuts are made progressively. However, both cuts may be made in one rotation of the cutter, so-

that the teeth of the desirable character de- -scribed areformed without loss in time.

The character of the invention may be best understood by reference to the following description of one good form thereof shown in the accompanying drawings, wherein Figure 1 is a ront elevation of a spiral Specification of Letters Patent.

',to furnish clearance.

patented Mar. d, 1919.

Application filed May 24, 1917. Serial No. 170,660.

cutter shown herein as embodying the invention;

Fig. 2 is a horizontatl section of the cutter' shown in Fig. l;

Figs. 3, e and 5 are diagrammatic views illustrating the operation of the cutter in forming curved teeth on a gear blank;

Flgs. 6, 7, 8 and 9 are views showing the relative positions of th'e cutter and gear blank in the course of the generation of involute gears;

Fig. 10 is a plan of -a machine for supporting and operating the cutter and blank for the production of teeth on the latter;

Fig. 11 is a vertical section taken on line 11-11 .of Fig. 10 the ear blank and master gear being shown part yinfsection 'and partly 1n elevation;

Fig. 12 is a perspective view of a pair'ioi y intermeshing gears havin curvedteeth produced by the cutter descri ed herein; and

Fig, 13 is `a perspective view of portionsv of thetable and bed showing a device for limiting movement of the former along the latter.

Referring to the drawings g-the cutter shown therein as embodying the invention comprises a disk head l (Figs. 1 and 2) mit the saine to be secured to a suitable driving spindle. On this head is mounted means for formingl the concave and convex proiiles of curved teeth.

To cut t-he concave profiles of the teeth,

lhaving a hub 3 internally threaded to perin the present instance of the invention, a

cutter 5 is provided on said head comprising a series of teeth, each having a forward cutting edge 9 and a body 1l tapered rearward anda final tooth 15 mark the limits of the series of teeth of the cutter 5 which may extend along .an-arc of substantially 180.

-The Iouter edges of the teeth are adapted to cut the concave profile of the tooth in a blank, and are on radii Iprogressively increasing in length from the leading to' the final tooth of .the series. The radius 7" of :fthe final tooth determines thev radius of thezconcave profile of the tooth.

To cut the convex proles of the teeth, in the present instance of the invention, a cutter 17 is provided on said head and comprising a series of teeth having forward cutting edges A leading tooth 13 same.

and tapered bodies similar tothe teeth of the cutter for forming the concave profiles of a tooth. The final tooth 15 of the cutter for makin the concave profiles of the teeth may constitute the leading tooth of the cutter for making the convex profiles of the teeth. The final tooth 19 marks the other limit of the cutter, which also may extend along an arc of substantially 180. The 1nner edges of these teeth. cut the convex profiles of the teeth and are on radii progressively increasing in length from the leading to the final tooth of the series, but the radius r of the final tooth 19,0f the convex profile cutter equals the radius 1' of the final tooth 15 of the concave profile cutter. Since the' vteeth 15 and 19 make the -final cuts in pro ducing the concave andv convex profiles respectively of a tooth, and are of equal radii, it follows that the curvature of the arcs of said concave and convex profiles lwill be the 1 The concave profile forming cutter and the convex profile forming cutter, in the present instance of the invention, are mounted on the same head, and are'progressively disposed,

so that -they make cuts successively along the concave and convex profiles, but complete' cuts are made on both profiles once in each rotation of the head.

It will .be noted that the outer edges of .ithe'fteethvof the concave lcutter 5 form the concave profiles of the teeth, whereas, the

inner edges of the convex-cutter 17 form the convex profiles of the teeth. The inner edges of the teeth' oftheconcave cutter 5 are radially outward from the inner edges of the teeth of the convex ycutter 17, and the outer edges of the teeth of the convex cutter are radially inward from the outer edges of the teeth of the concave cutter. As a result, the

outer edges of the teethof the concave cutter and the inner edges of the teeth of the' convex cutter, arev theonly edges which are active in formingy the yconcave vand convex profiles of 'the teeth;

The concaveand convex cutters, in the present instance of the; invention, are arranged on the head with one as a continuationof:` the otherand forming parts of the .same spiral, butso far as leither operation 1s concerned, they are lin effect, separate cutters.l The form of the cutters in the se- 'lected embodiment ofthe invention, is a spiral but not necessarily a spiral of Archimedes,.since various forms maybe adopted,` -provided the radii of the final teeth of the two cutters are equal to produce final cuts what above said'table.- The gear blank may i foot of the sleeve and the Vlower faceof the 'is employed, it is necessary to rotate the said spindle being adapted to be driven at different speeds by stepped belt pulleys 27.

The cutter may be used to produce teeth in different articles. In the present exemplification of the invention, it is' shown as used for cutting curved teeth in spur gears.

The gear blank 29 (Figs. 10 and 11) is supported in a horizontal plane transversely to the plane of the cutter. To accomplish this, a table 31 is mounted on a bed 33 supported on the standard and provided with a dove-tailed projection 35 adapted to slide in a similarly shaped guidevvay in said bed to allow the table to be moved inl a direc-Y tion parallel to the axis of the spindle. To feed the table, the usual screw 37 having a hand wheel`38 may be threaded in said table and confined agalnst axial movement relative to said bed. Inward movement of the table toward the cutter may be limited by a 8 screw 39 (Figs. 10 and 13) threaded inan ear 41 projecting from said bed and adapted to engage a lug 43 projecting from said table in line with said screw. v

To position the blank on the table, the 9 latter is provided with uprights 45 (Fig. 11,) having a bridge-bar 47 hinged to one and adapted to be locked to the other -by a swing bolt 49.

A mandrel 51 is vertically disposed be- 9 tween said uprights, and has conical ends adapted to set in conical bearings in an upper plug 53 threaded in Ysaid bridge-bar, and in a lower plug 55 threaded in said table. The upper plug may be adjusted to take up wear and secure the mandrel accuv rately in position Without lost motion.

TheY ear blank 'may be mounted on a sleeve 5 on' said mandrel, said sleeve having a foot 59 adapted to rest against the upper end of a boss bearing 61 projecting some- `be supported the appropriate distance above the table to be acted upon by the cutter by a' spacing washer 63 interposed between the As thespiral cutter is rotated, it is essential that the gear blank should be rotated. Vlhen a spiral cutter such as shown herein blank a distance equal to the pitch of a tooth to be formed on the blank, in the course of each rotation .of the cutter, and since the cutter is rotated continuously, the blank should be rotated continuously.

'To rotate the blank as described, a master gear (Figs. 10 and 11) maybe mounte on the sleeve sustaining the blank, and ma be spaced from the blank-by a Washer 67 To secure the'blank and master gear toth sleeve, a nut 69 may be threaded' on sai" sleeve adjacent the top thereof, and engag the upper end of a washer 71 interposed be tween said nut and master gear. Whe

[and the final tooth of the with an idler gear 87 the nut isv adjusted toward the foot of the., sleeve, it will c oniine'thelblank, the master gear, and the spacing Washers between them. Consequently, rotation of the l master gear Will be shared by tlieblank. 4

Suitable mea'ns may be provided for driving the master gear. In the present instance of the invention, thisv may be accomplished by a spiral gear 73 (Figs. 104and 11) fast on one end of a shaft 75 journaled in a bearing 77 mounted on the table referred to. An

elongated gear 79 fast on the opposite end of said shaft meshesA with a pinion 81 fast on a shaft 83 journaled in bearings in the uprights 23 referred to. The shaft 83 may driven by a gear 85 fast thereon meshing mounted on a stu shaft carried by one of the uprights 23, said idler gear being driven bya pinion 8-9 on the cutterspindle 21.

By the gear train described, the master gear may be conveniently driven from the cutter' spindle. 'When the table is fed toward the cutter, the'elongated gear 79 may slide along the gear 81 without loss of engagement therewith, so that the automatic driving of 'the master-gear may continue without interruption While the taible is fed toward the cutter.

In operation, the bridge-bar 47V is swung to its position shown in. dottedlines in Fig. 11, and the sleeve with the gear blank and master gear secured thereto is slid down onto the mandrel, and the bridge-bar is 'secured in. its position shown in full lines in Fig. l1. Then the spindle is rotated, thereby rotatin the cutter and the blank. Compre ension of the operation of the cutter may be facilitated by reference to the cycle of its operations illustrated in Figs.' 3, 4 and 5. In Fig. 3 the concave cutter 5 is shown with its leading tooth 13 starting to cut the concave profile of a tooth along the arc a-a. In Fig-4 the cutter has rotated through an arc of 180, thereby causing the series of teeth of the concave cutter 5 to perform their cuts, and bringing the nal tooth 15 to the position formerly occupied by the leading tooth 13.' The iinal tooth 1s nowl completing the concave profiler of the tooth radius r referred to.

cut along the and on the `'Ihe'inner edge ofthe linal tooth 15 constltutes a part of the convex cutter 17, and is shown commencing the convex cut along line b-b in Fig. 4. When the cutter rotates through an arc of 180, the leading'tooth carried around to their positions shown in Fig. 5, Where the final tooth is shown completing the cut along-the convex profile of the tooth on line lThis marks the completion of concave and convex profile cuts', and brings the concave cutter 5 back to the position which it had `at *the commencement convex cutter are be noted that as the linal tooth of the convex cutter is completing its cut, the leading tooth of the concave cutter is commencing a new concave cut along the line c-c. u 4

The linal 'tooth of the convex cutter completes its cut on the radius 7", which as stated, is equal to the radius r, and consequently, the arcs of the concave and convex profiles of the tooth have 'the same curvature.

The cycle of operations performed by the cutter during one rotation thereof, has just been described. The blank is rotated an increment equal toa pitch of one tooth to be cut on the gear -blank by rotation of the blank through the mast-er gear and the train of gears described, it being understood, that said train is appropriately designed to transmit the proper increment of rotation of the @32516. n will of the blank. Then the Stable may be fed inwardtoward the cutter, in order to produce deeper cuts in the blank. The table may be fed on and in toward the cutter until teeth in the blank of the required depth are completed. The screw 39 may be adjusted to engage the'stop lug 43 on the table at the proper time to automatically insure cutting teeth of the requisite depth.

The rotation of the gear blank and increment equal to the pitch of 'a tooth tobe formed on the blank, serves-.tol bring the blank progressively in relation'to the cutter to generate involute teeth. 'f This operation is illustrated in the diagr'ams'shown in Figs. 6, 7, 8 and 9. In

6 the cutter is shown commencing to enter the blank. In Fig. 7 the blank is shown in its position afterit is `rota-ted a distance equal to the pitch of the tooth, thereby partially prod-ucing't e curved profiles. In Fig. '8 the blank is shown fed sufficiently-in toward the cutter to produce teeth of the required depth. In Fig. 9 the blank is shown in its position'afterv being rotated a distance equal to the pitch of the tooth, thereby completing the involute profle'of the tooth. i"

After lthe teeth have been cut throughout the circumference of the blank, themachine is arrested, the bridge-bar is released, and the master gear, ear thus and the formed are removed from theirl supporting sleeve.` e'

It will be apparent that b 93 (Fig. 12) to accuratel as said concave profile.

' spiral toothed cutters thereon,

the gears 91 and y mesh With the convex profiles of the teeth of one of the gears engaging throughout the lengths of the concave profiles of the other gear. As a result, the full power of the teeth is utilized, the life of the gears is prolonged, and quiet operation is assured.

The active profile forming edges of the teeth of the concave and convex forming cutters, in the present instance of the invention, are substantially true spirals, while the opposuch gears, for example,

site edges of said cutters are offset outwardly.

and inwardly from continuations of said spirals indicated by broken lines in Fig. 1.

The cutter may not only be used to produce curved teeth of gears such as described, but also may be used to produce curved teeth on beveled gears and teeth on devices for other purposes as desired. f

It will be understood that the invention is not limited to the specific embodiment shown, but thatvarious deviations may be made therefrom, Without departing from the spirit and scope of the appended claims.

Claims:

1. A cutter comprising a member having aspiral cutter thereon or forming a concave profile of a tooth in a blank, and a spiral cutter on said member for forming a convex profile of said tooth. y

2. A cutter comprising a member having a spiral cutter thereon for forming a concave profile of a tooth cutter on said member for forming a convex profile of said tooth with the same curvature 3. A cutter `comprising spiral cutters thereon, one

other forcutting the convex profile of said tooth, said cutters having portions of equal radii for producing concave and convex profiles of the same curvature. i

4. A cutter comprising. a member having a tooth in a blank,

ing a concave profile of and the other for forming a convex profile of ylili saidtooth with the same curvature as said concave profile.

5. A cutter spiral cutters thereon and convex profiles of a tooth said cutters being progressively disposed on said member for making their cuts successively.

6. A cutter comprising a member having comprising a member having for forming concave the other.

inner edges for cutting the convex in a blank,-and a spiral a'member hav-ing for cutting the concave profile of'a tooth 1n a blank, and the' yforming the concave one for form- 'ing the concave tooth, the teeth of each series having proin a blank,

spiral cutters thereon for forming concave and convex profiles of a tooth in a blank, respectively, said cutters being relatively arranged on said head for making successive cuts in the course of one rotation of said member.

7. A cutter comprising a member having spiral cutters thereon for forming concave and convex profiles of a tooth in a blank, one of said cutters 8. A cutter comprising series of'spirally arranged teeth progressively disposed, one series for forming the concave profile and the other series for forming the convex' profile of a tooth.

9. A cutter comprising series of teeth spirally disposed, one of said series having outer edges for cutting the concave profile of a tooth and the otherV of said series having profileof the tooth.

10. A cutter comprising series of spirally disposed teeth, one of said series having outer edges for cutting the concave'profile of a tooth and the other of said series having inner edges for cutting the convex profile of the tooth, said series having inactive edges opposed tc said cutting edges.

11. A cutter comprising series of spirally disposed teeth, one of said series having outer edges for cutting 'the concave profile of a tooth and the other of said series having inner edges for cutting the convex profile of being radially offset from inner edges radial-ly outward 4from the inner edges of the second series, and the second series having outer edges radially inward from the outer edges of the first series.

12. A cutter comprising a pairof circumferentially disposed cutters for progressively and convex profiles of a tooth and having portions of equal radii for producing said proiles on arcs of the same curvature.

13. -A cutter comprising series of circumferentially disposed cutting teeth for formand convex profiles of a gressively increasing radii, and the nal teeth of both series having equal radii for finishing said profiles with the same curvature.

1n testimony whereof, I have signed my name to this specification,

WILLIAM Vc. i FARNUM. 

